A single nucleotide polymorphism (SNP) is a single base-pair mutation at a specific site in a genomic DNA sequence. SNPs are responsible for the majority of the DNA variations between two individuals. SNPs can predispose individuals to develop a certain disease or respond to a drug differently. Therefore, detection of SNPs can be used to monitor genetic conditions.
Gene variations and mutations also occur in pathogens, such as virus and bacteria. Detection of gene variations and mutations can be used to distinguish pathogens and in some cases can be helpful in predicting prognosis and course of treatment. Single base mutations also occur in somatic cells, for example during development and progression of cancer. Detecting these mutations is helpful in predicting response to therapy.